If you have ever read a headgasket replacement guide, most of them insist to get the head machined so the head is no longer warped (warped meaning not level) when it makes contact with the engine block. Skimming the head is removing more material than is needed to level the head to boost the compression.

I wouldn't know how much it would be worth...if you disassembled the head yourself it'd be pretty cheap. Definately sub $500, Im guessing 250ish. Get yourself a quote from a machinist shop.

Hey Froudey, ask around for a spare head of another car which is cracked or something. If you are ringing around, see if the engine shops have cracked heads that they are just throwing out, see if you can tax that off them and practice on those before attacking the good head.

Yeah!!!, how else did you think you were going to get it apart???You had better get a w/shop manual, eh?

i have a work shop manual for 3.9 series. is much if any differences from the 4L onwards?

i will price a spring compressing tool and purchase one when i have the cash. As i said before slow and steady...

Another queastion...If this head is any good and i go well what is the go with the whole compression issue.... (ie 3.9 raises a 4L compression and a 4L lowers the decompression) is this an issue at all, eg. lower the power out put or torque or even raise said things

One of the differences may be the size of the HLA's. They are very similar otherwise, just little things here & there.
When you raise the compression ratio, it increases the torque. But in doing this, there can be consecquences, like too higher compression, pinging ( detonation ), engine won't run properly due to the ECU trying to compensate in some way.
You usually raise the comp. ratio because your running a longer duration/higher lift cam.
There other delamers to concider when changing engine specs, like comp. ratio, cam profiles, piston types ( flat tops, lumpy tops, etc ), valve head sizes..etc, etc.....

To Busy at work to do a ring around... but i am thinking i will get the head shaved and just clean all parts and then polish it etc etc and put it back together not going to change any bits from OEM so in theory i shouldn't stuff anything around...

Froudey, I just finished reconditioning a 4L head for my car, I smoothed and polished exhaust and combustion chamber and slightly ported intake, then got head shop to chemical clean, flow test, shave, cut new valve seats, supply and fit new valve stem seals, supply new head bolts and gaskets, cost me $550, I got CMS to supply me new XR6 size exhaust valves and got an AU head gasket from ford, Total has estimated up to $850

Froudey, I just finished reconditioning a 4L head for my car, I smoothed and polished exhaust and combustion chamber and slightly ported intake, then got head shop to chemical clean, flow test, shave, cut new valve seats, supply and fit new valve stem seals, supply new head bolts and gaskets, cost me $550, I got CMS to supply me new XR6 size exhaust valves and got an AU head gasket from ford, Total has estimated up to $850

great thanks for that got something to go from....

at lunch hopefully will get it into the sun light have a look at it and on the weekend start distmantling it... this is just a hobby / learning experiance to rebuilt it to OEM specs or xr6 spec

I got of my a** finally and took the head out of the boot of my car and put in my garage on the bench and gave a quick once over seems to be no cracks i also gave it a hit with degreaser and bug and tare grease remover product and it is currently sitting and degreasing on tomorrow i start distmantling.

*Update going to purchase a set of spring compressors or find if i can borrow a set from father's best mate.. and then i will take the springs out and the pop round the corner and drop it off so it can be soda blasted (got quoted between 25 and no dearer then 35 dollars) so on tuesday next week i will have a nice clean head...

nah not from an lpg motored car, as far as i know it come from a car that had done around close to 400kms (Avis EB Falcon) Prior to taking the rockers off i just hit it with the hose and dried the water off.

I priced a set of spring compressor 65 dollars then i thought "well i wil prolly only use it twice max..." although it would be a handy thing to have and ad to my toolbox collection.

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